Finfet devices and methods of manufacture

ABSTRACT

A finFET structure and method of manufacture such structure is provided with lowered Ceff and enhanced stress. The finFET structure includes a plurality of finFET structures and a stress material forming part of a gate stack and in a space between adjacent ones of the plurality of finFET structures.

FIELD OF THE INVENTION

The invention relates to semiconductor structures and methods ofmanufacture and, more particularly, to a finFET structure with loweredCeff and enhanced stress and methods of manufacturing the same.

BACKGROUND

As integrated circuits continue to scale downward in size, the finFET(fin field effect transistor) is becoming an attractive device for usewith smaller nodes, e.g., the 22 nm node and beyond. In a finFET, thechannel is formed by a semiconductor fin and a gate electrode is locatedon at least two sides of the fin. Due to the advantageous feature offull depletion in a finFET, the increased number of sides on which thegate electrode controls the channel of the finFET enhances thecontrollability of the channel in a finFET compared to a planar MOSFET.The improved control of the channel allows smaller device dimensionswith less short channel effects as well as larger electrical currentthat can be switched at high speeds. A finFET device generally hasfaster switching times, equivalent or higher current density, and muchimproved short channel control than planar CMOS technology utilizingsimilar critical dimensions.

Two of the main detractors for realizing such finFET device technologyare the higher Ceff and ineffectiveness of conventional stress elementssuch as eSiGe or stress liner. Any innovation in device architecturewhich can reduce either of these components will help in improving theperformance of the finFET device circuits.

In order to reduce the high resistance of thin body Si, finFET orfrigates are typically merged in the source drain (S/D) area to reducethe external resistance. However, with such device integration, the Ceffof the device is higher since there is a finite gate-to-EPI capacitanceas the conductive part of the gate in non-fin areas and the EPI merge isseparated by the spacer. Such dead areas in the gate cannot be avoidedin finFET or trigates devices.

Accordingly, there exists a need in the art to overcome the deficienciesand limitations described hereinabove.

SUMMARY

In a first aspect of the invention, a finFET structure comprises aplurality of finFET structures and a stress material forming part of agate stack and in a space between adjacent ones of the plurality offinFET structures.

In another aspect of the invention, a finFET structure comprises aplurality of finFET gate structures comprising a gate material depositedon a dielectric material. The finFET structure further comprises aninsulator stress material provided in a space between each fin of theplurality of finFET gate structures and on sides of the fins. The finFETstructure further comprises a conductive layer on the insulator stressmaterial. The insulator stress material has a lattice constant differentthan that of the gate material used for the plurality of finFET gatestructures.

In yet another aspect of the invention, a method comprises formingfinFET gate structures by depositing gate material and dielectricmaterial on patterned fins. The method further comprises merging thefinFET gate structures by depositing and patterning insulative stressmaterial on sides of adjacent finFET gate structures.

In another aspect of the invention, a design structure tangibly embodiedin a machine readable storage medium for designing, manufacturing, ortesting an integrated circuit is provided. The design structurecomprises the structures of the present invention. In furtherembodiments, a hardware description language (HDL) design structureencoded on a machine-readable data storage medium comprises elementsthat when processed in a computer-aided design system generates amachine-executable representation of the coplanar waveguide structure(CPW), which comprises the structures of the present invention. In stillfurther embodiments, a method in a computer-aided design system isprovided for generating a functional design model of the CPW. The methodcomprises generating a functional representation of the structuralelements of the CPW.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention is described in the detailed description whichfollows, in reference to the noted plurality of drawings by way ofnon-limiting examples of exemplary embodiments of the present invention.

FIG. 1 shows a beginning structure and respective processing steps inaccordance with aspects of the invention;

FIGS. 2-6 show structures and respective processing steps in accordancewith aspects of the invention; and

FIG. 7 is a flow diagram of a design process used in semiconductordesign, manufacture, and/or test.

DETAILED DESCRIPTION

The invention relates to semiconductor structures and methods ofmanufacture and, more particularly, to a finFET structure with loweredCeff and enhanced stress and methods of manufacturing the same. Morespecifically, the finFET structure of the present invention includesstress material in non-fin areas. In embodiments, the stress materialcan be placed between the fins. In the integration scheme of the presentinvention, the Ceff of the device can be decreased as well as stress canbe imparted in the device using the stress material. In embodiments,imparting stress from the gate is very effective for finFETs since thegate wraps around the fins and the channel can be stressed from bothsides. The additional benefit of using stress materials is that suchstress materials are typically insulators (e.g., nitride) and hence, thegate-to-EPI capacitance of conventional systems is eliminatedcompletely.

In the present invention, the fins of the finFET are formed usingconventional fabrication processes, e.g., SIT (sidewall image transfer).The gate stack is formed on the fins by depositing and patterninginsulator material such as, for example, a high-K material, followed bygate material such as, for example, metal or poly. In case of materialssuch as TiN or TaN for the gate material, since the resistance of thematerial may present an issue, it can be followed by a high conductivitymetal which is used for decreasing the resistance of the metal gatealong the fin height. Post gate stack deposition, insulating stressmaterial is deposited, which stresses the channel directly from thegate. Using chemical mechanical polishing (CMP), for example, the stressmaterial is planarized stopping on top of the gate or the fin cap. Inorder to provide electrical connection to all the gates around thefinFETs, a conducting metal layer can be deposited and the gatespatterned. In embodiments, when the top of the gate structure is ametal, this will also help with forming borderless contacts.

FIG. 1 shows a beginning structure and respective processing steps inaccordance with aspects of the invention. The structure includes asubstrate 100 with a plurality of fins 102 comprising SOI material 104and an insulator material 106 such as, oxide. Although two fins areshown, it should be understood that the plurality of fins can be anynumber of fins, for a particular chip. The oxide material, for example,can be a hard mask or capping layer. In embodiments, the fins 102 can beformed by deposition of the SOI material and insulator material using,for example, a conventional deposition process such as a chemical vapordeposition. In embodiments, the SOI material 104 and insulator material106 can each be deposited to a thickness of about 30 Å; although otherthicknesses are contemplated by the invention.

Once the materials 104, 106 are deposited, a patterning process can beperformed to form the fins 102. The patterning process can be, forexample, a conventional SIT process or a lithographic and etchingprocess. In embodiments, the SIT process will increase the density ofthe fins 102. The patterning will form a space 108 between the fins 102.

FIG. 2 shows the deposition of a dielectric material 110 and a gatematerial 112 over the fins 102 and within the space 108. In embodiments,the dielectric material 110 can be deposited to a thickness of about 10Å to about 30 Å, and more preferably about 15 Å. The dielectric material110 can be a high k dielectric such as, for example, hafnium oxide.However, other dielectric materials 110 are also contemplated by thepresent invention such as, for example, oxide, silicon oxide, siliconoxynitride, silicon oxynitride, or any combinations thereof such as, forexample, a stack of dielectric materials. The gate material 112 can be,for example, deposited to a thickness of about 10 Å to about 100 Å. Inembodiments, the gate material 112 can be, for example, a metal (e.g.,TiN or TaN) or poly material.

The dielectric material 110 and the gate material 112 can be depositedusing conventional deposition methods such as, for example, CVD or ALDprocesses. In the case of a metal gate, the gate material 112 can bealso deposited using, for example, a conventional sputtering technique.In embodiments, a thin layer of metal such as, for example, aluminum canalso be deposited on the gate structure, also represented by referencenumeral 112. The thin layer can be deposited to a thickness of about 5Å; although other thicknesses are also contemplated by the presentinvention.

In FIG. 3, a cap material 114 is deposited on the gate material 112. Thecap material 114 is a stress material that is deposited on the gatematerial 112, including within the space (e.g., gap) 108 between thefins 102 and on sides of the fins 102 (e.g., surrounding the fins 102).In embodiments, the stress material 114 merges the fins 102 in thesource/drain areas and forms the gates. The cap material (stressmaterial) 114 is an insulator material that will have a lattice constantdifferent than that of the gate material 112. In embodiments, thelattice mismatch between the stress material 114 and the gate material112 will result in a stress formation between the fins 102 (within thegap 108). The stress material 114 can be, for example, a nitridematerial which fills the gap 108 between the fins 102. The stressmaterial 114 will eliminate the Ceff; in comparison to using an EPImaterial that will increase the Ceff of the device.

In FIG. 4, the stress material 114 is planarized using, for example, aCMP to near or onto the tops of caps 114 on the fins 102. Inembodiments, complete removal of the stress material 114 from over fins102 is optional. In embodiments, the gate material 112 and dielectricmaterial 110 can also be polished; although this is not critical inpracticing the present invention.

FIG. 5 shows a deposition of a conductive layer 116 on the planarizedstructure of FIG. 4. The conductive layer 116 can be, for example,tungsten or tungsten silicide, for example. The conductive layer 116 canalso be capped with a hard mask, in embodiments. The hard mask is alsorepresented by reference numeral 116.

In FIG. 6, the structure undergoes a patterning process to form thefinFET structure 500 of the present invention. The patterning can beperformed by, for example, using a gate conductor mask, and patterningusing a reactive ion etching (RIE) process. In this way, the gate stack102 a comprises the conductive layer 116, stress material 114, gatematerial 112, and dielectric 110. In embodiments, the patterned metalgate is the complete gate conductor for each finFET. Contact of thisgate to other circuitry is through patterned conductive layer 112,connecting at intersections 118.

The stress material 114 will be provided between the fin structures 102a and will form the gate, which will effectively eliminate Ceff andprovide stress to the structure between the fins 102 a. Additionally,the patterned gate material 112 need not be silicided, as the patternedconductive layer 116 will provide a high-conductivity path for circuitryfabricated using the processes of the present invention. Also, thepresence of the stress material 114 (i.e., insulating material) insteadof a conductive material such as doped silicon will lower capacitance aswell as impart stress through the gate thereby improving deviceperformance.

FIG. 7 is a flow diagram of a design process used in semiconductordesign, manufacture, and/or test. FIG. 7 shows a block diagram of anexemplary design flow 900 used for example, in semiconductor IC logicdesign, simulation, test, layout, and manufacture. Design flow 900includes processes, machines and/or mechanisms for processing designstructures or devices to generate logically or otherwise functionallyequivalent representations of the design structures and/or devicesdescribed above and shown in FIGS. 1-6. The design structures processedand/or generated by design flow 900 may be encoded on machine-readabletransmission or storage media to include data and/or instructions thatwhen executed or otherwise processed on a data processing systemgenerate a logically, structurally, mechanically, or otherwisefunctionally equivalent representation of hardware components, circuits,devices, or systems. Machines include, but are not limited to, anymachine used in an IC design process, such as designing, manufacturing,or simulating a circuit, component, device, or system. For example,machines may include: lithography machines, machines and/or equipmentfor generating masks (e.g. e-beam writers), computers or equipment forsimulating design structures, any apparatus used in the manufacturing ortest process, or any machines for programming functionally equivalentrepresentations of the design structures into any medium (e.g. a machinefor programming a programmable gate array).

Design flow 900 may vary depending on the type of representation beingdesigned. For example, a design flow 900 for building an applicationspecific IC (ASIC) may differ from a design flow 900 for designing astandard component or from a design flow 900 for instantiating thedesign into a programmable array, for example a programmable gate array(PGA) or a field programmable gate array (FPGA) offered by Altera® Inc.or Xilinx® Inc.

FIG. 7 illustrates multiple such design structures including an inputdesign structure 920 that is preferably processed by a design process910. Design structure 920 may be a logical simulation design structuregenerated and processed by design process 910 to produce a logicallyequivalent functional representation of a hardware device. Designstructure 920 may also or alternatively comprise data and/or programinstructions that when processed by design process 910, generate afunctional representation of the physical structure of a hardwaredevice. Whether representing functional and/or structural designfeatures, design structure 920 may be generated using electroniccomputer-aided design (ECAD) such as implemented by a coredeveloper/designer. When encoded on a machine-readable datatransmission, gate array, or storage medium, design structure 920 may beaccessed and processed by one or more hardware and/or software moduleswithin design process 910 to simulate or otherwise functionallyrepresent an electronic component, circuit, electronic or logic module,apparatus, device, or system such as those shown in FIGS. 1-6. As such,design structure 920 may comprise files or other data structuresincluding human and/or machine-readable source code, compiledstructures, and computer-executable code structures that when processedby a design or simulation data processing system functionally simulateor otherwise represent circuits or other levels of hardware logicdesign. Such data structures may include hardware-description language(HDL) design entities or other data structures conforming to and/orcompatible with lower-level HDL design languages such as Verilog andVHDL, and/or higher level design languages such as C or C++.

Design process 910 preferably employs and incorporates hardware and/orsoftware modules for synthesizing, translating, or otherwise processinga design/simulation functional equivalent of the components, circuits,devices, or logic structures shown in FIGS. 1-6 to generate a netlist980 which may contain design structures such as design structure 920.Netlist 980 may comprise, for example, compiled or otherwise processeddata structures representing a list of wires, discrete components, logicgates, control circuits, I/O devices, models, etc. that describes theconnections to other elements and circuits in an integrated circuitdesign. Netlist 980 may be synthesized using an iterative process inwhich netlist 980 is resynthesized one or more times depending on designspecifications and parameters for the device. As with other designstructure types described herein, netlist 980 may be recorded on amachine-readable data storage medium or programmed into a programmablegate array. The medium may be a non-volatile storage medium such as amagnetic or optical disk drive, a programmable gate array, a compactflash, or other flash memory. Additionally, or in the alternative, themedium may be a system or cache memory, buffer space, or electrically oroptically conductive devices and materials on which data packets may betransmitted and intermediately stored via the Internet, or othernetworking suitable means.

Design process 910 may include hardware and software modules forprocessing a variety of input data structure types including netlist980. Such data structure types may reside, for example, within libraryelements 930 and include a set of commonly used elements, circuits, anddevices, including models, layouts, and symbolic representations, for agiven manufacturing technology (e.g., different technology nodes, 32 nm,45 nm, 90 nm, etc.). The data structure types may further include designspecifications 940, characterization data 950, verification data 960,design rules 970, and test data files 985 which may include input testpatterns, output test results, and other testing information. Designprocess 910 may further include, for example, standard mechanical designprocesses such as stress analysis, thermal analysis, mechanical eventsimulation, process simulation for operations such as casting, molding,and die press forming, etc. One of ordinary skill in the art ofmechanical design can appreciate the extent of possible mechanicaldesign tools and applications used in design process 910 withoutdeviating from the scope and spirit of the invention. Design process 910may also include modules for performing standard circuit designprocesses such as timing analysis, verification, design rule checking,place and route operations, etc.

Design process 910 employs and incorporates logic and physical designtools such as HDL compilers and simulation model build tools to processdesign structure 920 together with some or all of the depictedsupporting data structures along with any additional mechanical designor data (if applicable), to generate a second design structure 990.

Design structure 990 resides on a storage medium or programmable gatearray in a data format used for the exchange of data of mechanicaldevices and structures (e.g. information stored in a IGES, DXF,Parasolid XT, JT, DRG, or any other suitable format for storing orrendering such mechanical design structures). Similar to designstructure 920, design structure 990 preferably comprises one or morefiles, data structures, or other computer-encoded data or instructionsthat reside on transmission or data storage media and that whenprocessed by an ECAD system generate a logically or otherwisefunctionally equivalent form of one or more of the embodiments of theinvention shown in FIGS. 1-6. In one embodiment, design structure 990may comprise a compiled, executable HDL simulation model thatfunctionally simulates the devices shown in FIGS. 1-6.

Design structure 990 may also employ a data format used for the exchangeof layout data of integrated circuits and/or symbolic data format (e.g.information stored in a GDSII (GDS2), GL1, OASIS, map files, or anyother suitable format for storing such design data structures). Designstructure 990 may comprise information such as, for example, symbolicdata, map files, test data files, design content files, manufacturingdata, layout parameters, wires, levels of metal, vias, shapes, data forrouting through the manufacturing line, and any other data required by amanufacturer or other designer/developer to produce a device orstructure as described above and shown in FIGS. 1-6. Design structure990 may then proceed to a stage 995 where, for example, design structure990: proceeds to tape-out, is released to manufacturing, is released toa mask house, is sent to another design house, is sent back to thecustomer, etc.

The method as described above is used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims, if applicable, areintended to include any structure, material, or act for performing thefunction in combination with other claimed elements as specificallyclaimed. The description of the present invention has been presented forpurposes of illustration and description, but is not intended to beexhaustive or limited to the invention in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the invention.The embodiment was chosen and described in order to best explain theprincipals of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated. Accordingly, while the invention has beendescribed in terms of embodiments, those of skill in the art willrecognize that the invention can be practiced with modifications and inthe spirit and scope of the appended claims.

1. A finFET structure, comprising: a plurality of finFET structures; anda stress material forming part of a gate stack and in a space betweenadjacent ones of the plurality of finFET structures.
 2. The finFETstructure of claim 1, wherein the stress material has a lattice constantdifferent than that of a gate material of the plurality of finFETstructures.
 3. The finFET structure of claim 2, wherein the stressmaterial is an insulator and the gate material is one of a poly andmetal material.
 4. The finFET structure of claim 1, wherein the gatestack comprises a conductive layer, the stress material, gate material,and dielectric material, in order.
 5. The finFET structure of claim 1,wherein the stress material is a nitride material.
 6. The finFETstructure of claim 5, wherein the plurality of finFET structurescomprises a gate material deposited on a dielectric material, and thestress material on the gate material.
 7. The finFET structure of claim1, wherein the stress material is provided on both sides of theplurality of finFET structures.
 8. A finFET structure, comprising: aplurality of finFET gate structures comprising a gate material depositedon a dielectric material; an insulator stress material provided in aspace between each of fin of the plurality of finFET gate structures andon sides of the fins; and a conductive layer on the insulator stressmaterial, wherein the insulator stress material has a lattice constantdifferent than that of the gate material used for the plurality offinFET gate structures.
 9. The finFET structure of claim 8, wherein theplurality of finFET gate structures includes a gate stack comprising theconductive layer, the insulator stress material, the gate material, thedielectric material, in order.
 10. The finFET structure of claim 8,wherein the insulator stress material is a nitride material.
 11. ThefinFET structure of claim 8, wherein the gate material is one of metalmaterial and poly material.
 12. The finFET structure of claim 8, whereinthe insulator stress material is provided on both sides of the pluralityof finFET gate structures.
 13. The finFET structure of claim 8, whereinthe insulator stress material merges the plurality of finFET gatestructures in source/drain areas.
 14. A method, comprising: formingfinFET gate structures by depositing gate material and dielectricmaterial on patterned fins; and merging the finFET gate structures bydepositing and patterning insulative stress material on sides ofadjacent finFET gate structures.
 15. The method of claim 14, wherein thepatterned fins are formed by depositing SOI and insulator material on asubstrate and patterning the SOI and insulator material.
 16. The methodof claim 14, wherein the patterned fins are formed by a sidewall imagetransfer process.
 17. The method of claim 14, wherein the gate materialand the dielectric material are deposited on the patterned fins and thestress material is deposited on the gate material in a space formedbetween the finFET gate structures.
 18. The method of claim 14, furthercomprising patterning the insulative stress material.
 19. The method ofclaim 14, wherein the insulative stress material has a lattice constantdifferent than the gate material.
 20. The method of claim 14, furthercomprising planarizing the insulative stress material and depositing aconductive material on the insulative stress material, prior to apatterning.